Analysing the mechanical behaviour of thermoformed dental clear aligners using acoustic emission technique

Abstract

Abstract Clear aligners have been widely preferred in recent years for aesthetically pleasant orthodontic treatments. However, their efficacy in treating dental malposition and malocclusion is yet to be studied extensively. Clear aligners are mostly made from thermoplastic materials that guarantee sufficient elasticity while lowering the plastic deformations during their use. This is to guarantee a stable level of forces acting on teeth to be repositioned. This work aims to get insight into the mechanical behaviour of these devices during their period of use, by comparing aligners produced from two different thermoplastic materials: polyethylene terephthalate-glycol modified (PET-G) and polyurethane (PU) supplied by Dooris and Ghost Aligners, respectively. The aligners were subjected to cyclic compression loading, to simulate the swallowing act throughout 15 days of use. Tests were conducted by surrounding the aligners with artificial saliva to simulate the intraoral environment. The Acoustic Emission (AE) technique was used to analyse the damage progression in the aligners during the loading. Furthermore, the AE results were compared with the energy absorbed and the stiffness changes in the aligners. Finally, the damage evolution in the aligners post-loading was validated using optical microscopy. The AE results revealed a good correlation with mechanical and optical microscopy data, thus contributing to the understanding of the mechanical behaviour of the clear aligners.